CWB level 3 Module 21 practice questions with verified answers

The maximum solubility of carbon in a iron is: (a) 2%. (b) 0.002%. (c) 0.02%. (d) There is no solubility. - ans ----(c) 0.02%. True or false? When a steel is heated into the austenite region, all carbon and most other compounds dissolve to form a single phase. - ans ----True True or false? Pearlite is a single phase. - ans ----False What is the resulting structure of a 0.6% carbon steel slowly cooled from 900°C to room temperature? - ans ----About 25% proeutectoid ferrite and 75% pearlite Most fine grain steels retain their fine grains: ( (a) up to the melting temperature. (b) up to the grain coarsening temperature, but above that behave as coarse grain steel. C (c) only up to the transformation temperature. - ans ----(b) Why is martensite produced rather than pearlite when a steel is rapidly quenched from, 900°C? - ans ----Insufficient time for carbon to diffuse to form carbides The hardness of martensite depends mainly on the: (a) alloy content. (b) rate of cooling.